(1) Field of the Invention
The present invention relates to an articulated transmission joint, having a large telescopic travel, in particular for an automobile.
The invention is in particular applicable to homokinetic transmission joints comprising a first element, or tripod element, provided with three arms disposed substantially radially relative to its axis and each partly surrounded by two roller segments whose radially outer surfaces, having a curved transverse contour, are in rolling and sliding contact with longitudinal tracks of a second element. Usually, the longitudinal tracks are formed on the inner side of a hollow element of generally cylindrical shape termed a "bowl element" or "barrel element" surrounding the tripod element.
(2) State of the Prior Art
Such a joint is disclosed in the unpublished French patent application No. 86 17044 in the name of the Applicant. This joint has excellent features of comfort and compactness. It is simple and cheap and therefore very competitive.
In service, the movements of each arm of the tripod element, as resulting from the telescopic movement of the joint, or from the operation at a flexing angle of the joint, result in principle in a non-sliding rolling of the roller segments on their respective rolling track. This rolling movement is such that, when an arm of the tripod element travels toward either of the ends of its axial travel in the barrel element, the associated roller segments move away toward the rear of the arm relative to the considered direction of axial movement. This in principle permits giving to the joint a reduced axial overall size for a given movement capacity.
However, this capacity of movement, defined by the extent of the angularity-sliding diagram, depends on the reliability with which the roller segments take up their well-defined position corresponding to their minimum axial overall size when the joint is at the end of its compression or extension travel.
In order to ensure this reliability, the aforementioned patent application proposes meshing the roller segments with racks provided in the barrel element along the rolling tracks. However, the racks only allow the telescopic movement by the rolling of the roller segments, which limits the telescopic travel substantially to the circumferential length of the toric outer wall of the roller segments. This is counter to the intended objective, which is to provide the longest possible sliding length for a given angularity and diameter of the joint.